1. Field of the Invention
The present invention is directed generally to communication systems and, more particularly, to techniques for a push-to-talk communication system in an orthogonal frequency division multiplexed network.
2. Description of the Related Art
Public wireless networks, which usually have wide and ubiquitous coverage, can be useful in providing private network-type capabilities. Public networks based on iDEN technology, for example, offer the ability to provide push-to-talk capabilities similar to those in a private land mobile two-way network without the cost of building such a network.
The difficulty in providing two-way like services on a public wireless network, such as GSM, TDMA, and the like, is synchronization of all mobile units so that all mobile units receive a message simultaneously. It is important for this Group Call function to be synchronized so that all units can act on a command at the same time. For example, a SWAT team preparing to simultaneously enter the front and back entrances of a building would want both entry teams to receive the commands to enter at exactly the same time. This simultaneity has been an issue for networks that use data packet technologies. Variations in data packet timing across the network and over the airlink make simultaneous reception unpredictable. Some systems attempt to synchronize transmissions by establishing a phone call and conferencing all the mobile units together. This technique is limited by the amount of time it takes to establish the phone call so that while communication is simultaneous, the setup of the call means a lag between pushing the button to talk and the actual establishment of the communication path. Neither of these techniques accurately replicates the experience of push-to-talk on a private two-way network.
The iDEN system remedied the drawbacks of traditional public wireless networks by placing all receiving units for a Group Call in receive mode at the same time. The iDEN network uses a time division technique which divides all communications into slices of time called timeslots. By directing all of the mobile units in a Group Call into a single timeslot containing the communications, all units receive the same communications at the same instant.
Such techniques are not applicable to other forms of communication. Specifically, it can be appreciated that there is a significant need for a system and method for push-to-talk communication in an orthogonal frequency division multiplexed system. The present invention provides this, and other advantages, as will be apparent from the followed detailed description and accompanying figures.